Not having direct access to voice mail from within Smart Dial is what kills it for me. The dialer needs to replace the built-in dialer, having all the major features, or I have to use both. Using both is a major PITA.
And that's an argument I don't follow. Have two icons side by side. For all outbound calls use Smart Dial, if you have a voicemail use the other. No trouble. The only pain is the loss of Homescreen space, which I grant you, is a bit of a pain. But from a functional point of view there is no PITA aspect.